1. Field of the Invention
The present invention relates to a magnetic recording medium having excellent surface property and maximum residual magnetic flux density. More particularly, it relates to a magnetic recording medium comprising vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer or vinyl chloride-vinylidene chloride copolymer having up to 300 of polymerization degree as a component of a binder for a magnetic layer.
2. Description of the Prior Arts
The magnetic recording media such as magnetic tapes and magnetic cards are usually prepared by forming a magnetic layer on a substrate such as a film made of polyvinyl chloride, polyester or polycarbonate by bonding a magnetic powder such as .gamma.-Fe.sub.2 O.sub.3 with a binder. Various magnetic recording media have been proposed.
Recently, higher characteristics as improvement of electromagnetic convertible characteristic and high recording density have been further required depending upon an increase of fields of usages of such magnetic recording media. Certain vinyl chloride type copolymers have been used as the binder for this purpose. These copolymers have a polymerization degree of about 350 to 450. In the magnetic powder compositions comprising such copolymer, a content of the binder for an optimum printability is in a range of about 7.0 to 12%. Thus, a content of a solvent in the magnetic powder composition containing a magnetic powder is in a range of about 59.5 to 72.7%. Such high content of the solvent in the magnetic powder composition is disadvantageous in view of improvement of a surface property and a maximum residual magnetic flux density of the magnetic recording medium.